Idling Engines ramp up pollution
Streets full of stationary vehicles with their engines running could be 10 times more polluted than busy roads full of slow-moving traffic, new research has revealed.
Such streets could also be warmer than surrounding urban areas by as much as five degrees Celsius, according to a study by the South China Morning Post. Environmentalists said the research could provide useful clues as to the effectiveness of a ban on idling engines, which takes effect in December.
Using a handheld device capable of measuring the carbon monoxide level every two seconds, readings were taken in seven streets in Causeway Bay and Mong Kok on the afternoon of August 13, while a very-hot-weather warning was in effect.
A section of Tung Choi Street in Mong Kok between Argyle Street and Fife Street - where dozens of minibuses were idling - had the highest carbon monoxide reading, at 23,223 micrograms per cubic metre of air.
While that was below the maximum level of carbon monoxide set in the government's air quality objectives, which is 30,000mcg, it was up to 12 times higher than the reading on a stretch of nearby Fife Street, where traffic was sporadic and there were no idling vehicles. It was also 30 times the level recorded by the Environmental Protection Department's Mong Kok air quality monitoring station, near Nathan Road in Prince Edward, at the time.
At a bus stop on Nathan Road, near Fife Street, the Post recorded a carbon monoxide concentration of 2,450mcg.
Readings were also taken at Lockhart Road, Causeway Bay, between Cannon Street and Percival Street. One side of the road is a minibus terminus and the other is often occupied by private vehicles. The carbon monoxide level there was 8,285mcg, while a maximum temperature of 38 degrees was recorded, 5 degrees higher than at the Observatory.
Dr Lau Ngai-ting, of the environment division at the University of Science and Technology, said the results indicated serious pollution, although other environmental factors could have affected the findings.
James Middleton, from campaign group Clear the Air, said Tung Choi Street was a perfect example of the city's urban canyon effect, whereby walls of tall buildings prevent pollutants from being dispersed.
But he said poor maintenance of minibuses was also to blame.
'Carbon monoxide can be produced if an appliance hasn't been properly maintained or serviced regularly. How often do you think Hong Kong minibus owners service their vehicles? The correct answer is zero.'
Middleton said busy areas should be turned into low-emission zones in which only hybrid or electric buses would be allowed.
The Environmental Protection Department said the long-awaited ban on idling engines, first suggested in the 1990s, could cut roadside emissions by 1 per cent and help reduce nuisance to passers-by.
Environmentalists say the effectiveness of the ban will still be difficult to assess because the benefits could be offset by emissions from moving traffic nearby.
Lau said much more sophisticated studies would be needed to ascertain exactly how much of a contribution idling engines made to pollution and to evaluate the effectiveness of the ban on idling engines.
'The pollution may not necessarily come from the idling engine alone, as the moving traffic, the wind speed and direction and the urban topography will all have a role to play,' he said.
Lau said it was difficult to pinpoint why such a high reading was recorded in Tung Choi Street. It might be down to the ageing, slow-moving minibuses spewing more fumes, and also the poor air ventilation at the street, he said.
From December, drivers who leave their engines idling will face a fixed penalty of HK$320.
Air quality has long been a cause of concern for Hong Kong. In May, Chief Executive Donald Tsang Yam-kuen promised to set out new air quality objectives this year to replace the current rules, set in 1987.